To meet the demand for wireless data traffic having increased since deployment of 4G communication systems, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘Beyond 4G Network’ or a ‘Post LTE System’.
The 5G communication system is considered to be implemented in higher frequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To decrease propagation loss of the radio waves and increase the transmission distance, the beamforming, massive multiple-input multiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna, an analog beam forming, large scale antenna techniques are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud Radio Access Networks (RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), reception-end interference cancellation and the like.
In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.
For channel estimation, the transmitter and receiver share mutually agreed information. The receiver performs channel estimation based on such shared information. Schemes for channel estimation may be based on preambles or scattered reference symbols (scattered RSs). In embodiments of the present disclosure, channel estimation schemes based on scattered reference symbols are considered.
FIG. 1 illustrates a structure of subcarrier-reference symbol mappings for channel estimation based on scattered reference symbols in the quadrature amplitude modulation-orthogonal frequency division multiplexing (QAM-OFDM) system according to the related art.
Channel estimation based on scattered reference symbols for the QAM OFDM system is used in a cellular environment such as long term evolution (LTE).
Referring to FIG. 1, RS 110 is mapped to a particular subcarrier on a periodic basis so that channel information for the subcarrier is estimated. The channel information for all the subcarriers may be estimated through interpolation from the channel information estimated for the subcarrier.
FIG. 2 illustrates a structure of subcarrier-reference symbol mappings for channel estimation based on scattered reference symbols in the offset quadrature amplitude modulation (OQAM) OFDM system according to the related art.
Referring to FIG. 2, for channel estimation based on scattered reference symbols in a transmission system using OQAM and filters, auxiliary pilot 230 is used together with RS 210 to remove interference affecting RS 210 from neighboring subcarriers and symbols. Channel information at the position of RS 210 is estimated by using both RS 210 and auxiliary pilot 230, and the channel information for all the subcarriers may be estimated through interpolation from the channel information estimated at RS 210.
Owing to characteristics of transmitter and receiver filters in a cellular environment based on QAM filter bank multicarrier (FBMC) transmission, existing schemes for scattered RS based channel estimation applied to a cellular environment based on QAM-OFDM transmission like LTE are not readily applicable to the cellular environment based on QAM-FBMC transmission. As such, equalization performance may also be degraded.
Schemes for scattered RS based channel estimation applied to a cellular environment based on OQAM-OFDM transmission where one filter is used in the transmitter and receiver are not readily applicable to a cellular environment based on QAM-FBMC transmission where signal detection is performed differently from that for the OQAM-OFDM system and two different filters are used. In addition, schemes for scattered RS based channel estimation applied to the cellular environment based on OQAM-OFDM transmission uses auxiliary pilots besides RSs to estimate channel information for RSs, reducing frequency utilization efficiency.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.